Sensor and guide wire assemblies can be used to collect intravascular data using measurement sensors located at or near their distal tips. These devices are typically used in applications to measure internal properties of tissues and fluids such as blood pressure. Sensor and guide wire assemblies may be introduced into arteries, veins or other body organs either by themselves or through catheters that have been previously positioned within a patient. These assemblies can be used to measure pressure and other parameters.
For example, such assemblies can be used along with one or more pressure sensing devices such as a delivery catheter to measure a Fractional Flow Reserve (FFR) using pressure data. In addition, Coronary Flow Reserve (CFR) measurements can be performed using a thermodilution-based approach. In such an approach a CFR value is obtained by injecting a cold saline solution into the coronary artery of interest and using a temperature sensor to measure the onset of cold saline injection into the artery to the return of the temperature to a specific level.
The thermodilution method has a number of constraints. The stated accuracy of this method is as low as +/−30%. Further, the procedure is cumbersome/time-consuming, requiring a number of saline injections of a certain quality to produce enough data for the system software to calculate the CFR value. Performing FFR and CFR is performed as two separate methods given the nature of the thermodilution system, saline delivery, and subsequent measurements required.
FFR is used to provide a measure of stenosis severity in a coronary artery. The typical method to determine FFR is to measure a pressure drop in the coronary arteries at hyperemia. A hyperemia inducing substance is injected to create an increase in blood flow in the coronary system for a controlled period. The pressure drop is measured during this time period and used as an input in determining FFR.
In part, the disclosure relates to methods, systems and devices suitable for measuring FFR, CFR, and other values and generating diagnostic outputs that overcome some of the challenges with existing methods.